The present invention relates to a start control system for an alcohol engine capable of readily starting the engine by enhancing vaporization of a fuel to be supplied to the engine.
Because of possible shortage of fuel and the demand for purifying exhaust gas, the system using both gasoline and alcohol as the fuel has been practically used. A vehicle using this system (hereinafter called a Flexible Fuel Vehicle (FFV)) runs by using not only gasoline but also a mixed fuel of gasoline and alcohol, or only alcohol. The alcohol concentration (content) of a fuel used by FFV changes from 0% (only gasoline) to 100% (only alcohol) depending upon the circumstances of fuel supply.
An alcohol fuel has characteristics of a hard vaporization at a low temperature as compared with a gasoline fuel, a large latent heat of vaporization, a high flashing temperature, and the like. The engine output performance changes considerably with the alcohol concentration depending upon engine temperature at that time. Especially, there is a problem that the low temperature start performance is degraded at a high alcohol concentration.
There is known a technique dealing with the above problems, wherein the start performance can be improved by enhancing the vaporization of a fuel by using heating means such as a heater. For instance, there is disclosed in Japanese Patent Laid-open Publication No. 57-52665 the technique according to which a heater for heating an air intake pipe is controlled in accordance with an output from an alcohol concentration sensor in such a way that the calorific power of the heater is increased when the alcohol concentration becomes equal to or larger than a preset value.
The calorific power of the heater required for starting an engine changes largely with the engine temperature. Accordingly, if the calorific power of the heater is determined merely by the alcohol concentration, there is a possibility of failing to start an engine at a low temperature.
Further, if the calorific power is made large at a low engine temperature, electric power may be consumed wastefully when the atmospheric temperature rises or when the alcohol concentration lowers.